Response Of Astrocytes To Occlusal Trauma In Rat Spinal Trigeminal Nucleus Caudalis And Hippocampus

Traumatic occlusion causes a variety of deleterious effects both to local dental and masticatory system. Recent years, it has been improved that traumatic occlusion has effects on the sensitization and conduction of primary sensory neurons. AS constitutes nearly half of the total CNS. Recent years, an increasingly important role of the AS has been revealed. More and more evidences have shown that the AS has quite a few functions neglected before in pain and other noxious stimulation.Glial fibrillary acidic protein(GFAP), produced as an intermediate filament protein, has been widely used to monitor astrocyte reactivity in response to nociceptive stimulation. Activated AS can produce and release proinflammatory cytokines (tumor necrosis factor, interleukin-1, interleukin-6) and neuroactive substances (leukotrienes, excitatory amino acids). These substances regulate the conduction of noxious stimulation together. Our study investigates the response and relationship of astrocytes and neurons to orofacial pain induced by occlusal trauma.Mirror pain and extra-teritorial pain are two puzzling pain phenomena before. Now it has been revealed the role of the two pain phenomena is on the activated AS and the cytokines released by activated AS. Our study observes the change of astrocytes and cytokines in order to reveal the possible role of extra-territorial pain phenomena induced by occlusal trauma.Hippocampal formation plays an important role in spatial memory,learning and behavior. Recent years, a few studies show that hippocampal formation is also the brain region that is most sensitive to pain. It has been revealed that occlusal trauma induces orofacial pain. In our previous experiment, we found that occlusal trauma changed the behavior of the experimental animals. Our study investigates the change of GFAP within the hippocampal region during occlusal trauma.1. Effects of occlusal trauma on behavior and weight gain of ratsObjective: To establish an animal model of traumatic occlusion in rats and observe changes on activity and body weight gain.Methods: The occlusal surface of the left first maxillary molar was raised 0.5-0.8mm by bonding an orthodontic square wire to the tooth with methylmetacrylate resin. The changes on behavior and body weight gain were observed.Results:(1) Abrasion and widen periodontium ligament were detected on x-ray photos.(2) Occlusal trauma effected the behavior of rats.(3) Body weight gain of rats was suppressed by occlusal trauma.Conclusion: Occlusal trauma effected behavior and suppressed weight gain of rats.2. Response and relationship of astrocytes and neurons in rat Sp5C to occlusal traumaObjective: To investigate the changes of GFAP and cytokines in the Sp5C and the relationship between astrocytes and neurons during occlusal trauma. To study the effect of occlusal trauma on astrocyte and the mechanism of pain induced by occlusal trauma.Methods: Immunofluorescence histochemical was used to examine the distribution of GFAP in the Sp5C during the occlusal trauma. The expressions of GFAP mRNA in Sp5C were tested by RT-PCR technology.Results:(1) The number of GFAP-containing astrocytes decreased in Sp5C at 1 d after occlusal trauma, but increased at 3d; the maximum density of GFAP immunoreactivity in experimental side was found at 7d and returned to the control level at 4w. The number of GFAP-containing astrocytes increased in control side was less than that in experimental side.(2) The number of c-fos-containing neurons increased significantly in experimental side of Sp5C at 7d after occlusal trauma; the maximum density of c-fos immunoreactivity was found at 2w after occlusal trauma and returned to the control level at 4 week.(3) Comparing to the control group, the gene expression of the GFAP, IL-1, TNF α mRNA, were up-regulated at Id and reached peak level at 3d. The expression of nNos mRNA was significantly up- regulated at 14d and returned to control level at 4w.Conclusion: Both mRNA and protein level of GFAP increased in Sp5C in rats during the occlusal trauma. The peak value of GFAP was prior to that of c-fos. Significant elevated expression of IL-1, TNF α , nNos, GFAP mRNA in Sp5C and the increase in astrocytes GFAP-IR implied the possible involvement of astrocyte and cytokines in traumatic occlusal pain.3. The changes of astrocytes in hippocampus during occlusal trauma in ratsObjective: To observe the changes of GFAP in the hippocampus during occlusal trauma. To investigate the role of hippocampus in occlusal trauma.